1. Field of the invention
The present invention relates to a controller for driving current of a semiconductor device, and more particularly to a controller for driving current of a semiconductor device which can provide a constant amount of current to a memory device although the voltage level of an external voltage applied from an exterior changes.
2. Description of the Prior Art
Semiconductor devices show a tendency of having high integration and using lower power. In order to achieve the high integration of the semiconductor device, the size of internal elements contained in the semiconductor device becomes smaller and smaller. In addition, in order to achieve the low power, the semiconductor device drops an external voltage to a predetermined voltage level by using an internal voltage generation device contained therein, and uses the dropped voltage as a power supply voltage for internal elements. Since the internal elements are driven by such a power supply voltage having a low voltage level, power consumption of the semiconductor device decreases, but the operational speed of the internal elements decrease, thereby deteriorating the driving capability of the semiconductor device.
Also, according to the high integration of the semiconductor device, many internal elements simultaneously operate at one time, so that the driving capabilities of the internal elements are deteriorated when the power supply voltage used for the operations of the internal elements have a low voltage level. In order to prevent the driving capabilities of the internal elements from being deteriorated due to such a low voltage level of the power supply voltage, over-driving for the internal elements of the semiconductor device is performed. That is, when the voltage level of a power supply voltage applied to the internal elements of the semiconductor device is lower than a predetermined voltage level, an external voltage having a higher voltage level than that of the power supply voltage is applied to the internal elements in order to drive the internal elements.
For example, in a read operation of a semiconductor device, when a plurality of sense amplifiers operate at the same time in order to sense data stored in a memory cell, the sense amplifiers consumes a large amount of power in a moment due to the simultaneous operations of the multiple sense amplifiers. When these multiple sense amplifiers operate with a power supply voltage having a low voltage level, the driving capabilities of the multiple sense amplifiers are deteriorated and the voltage level of the power supply voltage is momentarily deteriorated. Also, in an initial read operation of the semiconductor device, when a plurality of sense amplifiers operate at the same time with a power supply voltage having a lower voltage level than a predetermined level, the multiple sense amplifiers cannot normally operate due to the power supply voltage having the lower voltage level than the predetermined level.
In order to solve such a problem, the sense amplifier of the semiconductor device is over-driven when the semiconductor device performs a read operation. That is, when the voltage level of the power supply voltage is lower than a predetermined voltage level, an external voltage having a higher voltage level than the power supply voltage applied to the multiple sense amplifiers. In other words, as shown in FIG. 1, the conventional semiconductor device supplies a power supply voltage Vcore and an external voltage Vdd, which have different voltage levels, to a sense amplification section 110 including a plurality of sense amplifiers 111, 112 and 113. Herein, the external voltage Vdd is a voltage provided from the outside of the semiconductor device, and the power supply voltage Vcore is an internal voltage obtained by dropping the external voltage Vdd to a predetermined voltage level by means of an internal voltage generation device contained in the semiconductor device. In FIG. 1, a first and a second control signal ‘sap’ and ‘san’ are signals for operating the sense amplifiers 111, 112 and 113 sensing and amplifying data stored in a memory cell when the semiconductor device performs a read operation. A third control signal ‘ovd’ is a signal for applying the external voltage Vdd to the sense amplifiers 111, 112 and 113 in order to improve the driving capabilities of the sense amplifiers 111, 112 and 113, when the sense amplifiers 111, 112 and 113 operate at the same time. That is, the third control signal ‘ovd’ is a signal for over-driving the sense amplifiers 111, 112 and 113.
In other words, when a plurality of sense amplifiers 111, 112 and 113 operate at the same time in order to sense and amplify data stored in a memory cell, the first and second control signals ‘sap’ and ‘san’ for operating the sense amplifiers 111, 112 and 113 are applied to a first and a second transmission means 121 and 122. The first control signal ‘sap’ enables the first transmission means 121 to provide the power supply voltage Vcore to each of the sense amplifiers 111, 112 and 113 of the sense amplification section 110, and the second control signal ‘san’ enables the second transmission means 122 to connect each of the sense amplifiers 111, 112 and 113 of the sense amplification section 110 to a ground node. Therefore, each of the sense amplifiers 111, 112 and 113 senses and amplifies data stored in the memory cell by the power supply voltage Vcore. In addition, when the third control signal ‘ovd’ is applied to a third transmission means 123, the third transmission means 123 provides the external voltage Vdd to each of the sense amplifiers 111, 112 and 113 of the sense amplification section 110.
As described above, in a read operation of the semiconductor device, when a plurality of sense amplifiers 111, 112 and 113 operate at the same time in order to sense and amplify data stored in a memory cell, the power supply voltage Vcore and the external voltage Vdd are supplied to each of the sense amplifiers 111, 112 and 113 of the sense amplification section 110 by the first and the third transmission means 121 and 123. As a result, the driving capabilities of the sense amplifiers 111, 112 and 113 are improved, so that the read operation of the semiconductor device is efficiently performed.
However, when the voltage level of the external voltage Vdd provided to the sense amplifiers 111, 112 and 113 through the third transmission means 123 is higher than a voltage level required for the efficient operation of the sense amplifiers 111, 112 and 113, the amount of current ‘i1’ flowing through a node connecting the first and third transmission means 121 and 123 and the sense amplifiers 111, 112 and 113 rapidly increases. The increase of the current ‘i1’ cause a noise to cause a malfunction of the sense amplifiers 111, 112 and 113, so that the semiconductor device may malfunction. Also, when the voltage level of the external voltage Vdd is lower than the voltage level required for the efficient operation of the sense amplifiers 111, 112 and 113, the amount of current ‘i1’ flowing through the node connecting the first and third transmission means 121 and 123 and the sense amplifiers 111, 112 and 113 decreases, thereby deteriorating the driving capabilities of the sense amplifiers 111, 112 and 113. Accordingly, a read operation of the semiconductor device may not be performed smoothly.
As described above, according to the conventional semiconductor device, the amount of current ‘i1’ applied to the sense amplifiers 111, 112 and 113, which operate with the external voltage Vdd and the power supply voltage Vcore provided thereto, changes depending on the change of the voltage level of the external voltage Vdd. Therefore, the sense amplifiers 111, 112 and 113 may malfunction due to the changing current ‘i1’. That is, the amount of current ‘i1’, which is provided to a load means of the semiconductor device operating with the external voltage Vdd, changes depending on the change of the voltage level of the external voltage Vdd, thereby causing a malfunction of the semiconductor device.